The present invention relates to an alarm system and method for detecting drowsiness of an automotive vehicle driver and delivering an alarm to keep the driver awake or, in turn, to recommend to the driver to take a rest in the interest of safety. More particularly, the present invention relates to a drowsiness alarm system for an automotive vehicle driver which detects drowsiness by way of observation of the driver's steering behavior.
During relatively long driving periods, for example, long-distance highway cruising, a vehicle driver is apt to face drowsiness at the wheel. If the vehicle driver dozes or feels intensely drowsy, driving behavior distinct from normal waking conditions will occur. Therefore, driver drowsiness can be detected by detecting such abnormal driving behavior.
Various approaches have been proposed in pursuit of reliable recognition of steering behavior due to driver drowsiness.
For example, the co-pending U.S. patent application Ser. No. 304,254, filed on Sept. 21, 1981, now U.S. Pat. No. 4,463,347, the corresponding European patent application of which has been published as Published European patent application No. 0048492, discloses a drowsiness alarm system which detects quick or abrupt steering operations and produces an alarm in response to the number of abnormally abrupt steering operations exceeding a predetermined value.
The Published European patent application No. 0049522 discloses a drowsiness alarm system for a vehicle which delivers an alarm to the vehicle driver to prevent driving in an increasing state of drowsiness. According to that invention, a drowsiness alarm system comprises a steering angle pulse generation circuit which produces first and second angle pulses whenever the steering wheel is rotated clockwise and counterclockwise, respectively, through a predetermined angular increment, a curved road detection circuit, responsive to the first and second steering pulses, which counts the number of the first and second steering pulses separately and judges that the vehicle is travelling on a curved road when the counted number of either of the first and second steering pulses reaches a first predetermined number within a predetermined period of time or when the difference between the counted numbers of the first and second steering angle pulses reaches a second predetermined number within the predetermined period of time, a first counting circuit which counts the number of the first and second steering angle pulses within the predetermined period of time and outputs a first alarm signal whenever the counted number reaches a third predetermined number, a second counting circuit responsive to the curved road detection circuit which counts the number of the first and second steering angle pulses and outputs a second alarm signal whenever the counted number reaches a fourth predetermined number greater than the third predetermined number, and an alarm unit which delivers an alarm to the driver in response to the first and second alarm signal.
The co-pending U.S. patent application Ser. No. 326,392, now U.S. Pat. No. 4,496,938, the Japanese counterpart of which has been published as the Published Japanese Pat. No. 56-2226, discloses a drowsiness alarm system for a vehicle which detects the driver's increasing state of drowsiness on the basis of abnormal steering change repetitions for a fixed period of time in a monotonous driving state defined, for example, by the gear shift lever being in the overdrive or top position. The alarm system produces an alarm to the driver to prevent the driver from allowing himself to become more drowsy. The drowsiness alarm system disclosed therein comprises: (a) a steering signal generator which generates a signal corresponding to the angle through which the steering wheel is rotated; (b) a monotonous driving-state detector which detects and signals that the vehicle is travelling in a monotonous driving state; (c) a discriminator which compares the change of steering signal level from said steering signal generator with a reference value for a fixed period of time; and (d) an alarm pulse generator which outputs an alarm pulse into an alarm circuit producing an alarm in response to the input alarm pulse when the output signal from the discriminator indicates that the change of steering signal exceeds the reference voltage throughout the fixed period of time.
The co-pending U.S. patent application Ser. No. 326,393, the Japanese counterpart of which has been published as Published Japanese Pat. No. 56-2225, discloses an alarm system for a vehicle driver to prevent same from dozing at the wheel. The system includes means for detecting driver drowsiness on the basis of abnormal steering change repetitions for a fixed period of time in a monotonous driving state defined, for example, by the transmission being maintained at an over-drive or top gear. The alarm system produces an alarm to the driver to prevent the driver from allowing himself to become more drowsy. The drowsiness alarm system disclosed therein comprises a steering signal generator which generates a signal corresponding to the angle through which the steering wheel is rotated, a monotonous driving-state detector which detects and signals that the vehicle is travelling in a monotonous driving state, a discriminator which compares the change of steering signal level from said steering signal generator for a fixed period of time with a reference value, and an alarm pulse generator which sends an alarm pulse to an alarm circuit producing an alarm in response to the input alarm pulse when the output signal from the discriminator indicates that the change of steering signal exceeds the reference voltage throughout the fixed period of time.
The Published European patent application No. 0059225 discloses a warning device for a vehicle which comprises a steering angle detector producing steering angle pulses indicative of the steering angle and the steering direction whenever the variation of the steering angular position exceeds a predetermined angle, a dozing detecting circuit which recognizes that the driver is alert when relatively frequent steering operations in one direction are performed and that the driver is dozing when steering adjustments which do not exceed the predetermined angle in one direction are repeated at a rate greater than a predetermined frequency in which case it outputs a warning signal, and a warning means for producing a visible or audible warning in response to the warning signal, whereby the warning device can accurately detect dozing of the driver and produce a warning to make the driver wake up.
The Published European patent application No. 0060306 discloses a warning device which detects abrupt steering when the driver is dozing at the wheel and in such cases, delivers a warning. The warning device comprises a sensor for detecting steering variation angle, a circuit for detecting abrupt steering based on detected right- and left-hand steering angle variations, and circuits for operating a warning means when consecutive abrupt steering adjustments to the left and to the right are detected within a given period.
The Published European patent application No. 0061501 discloses a warning device for a vehicle which comprises a steering angle detector producing steering angle pulses indicative of the steering angle and the steering direction whenever the variation of the steering angular position exceeds a predetermined angle, a dozing detecting circuit which recognizes that the driver is alert when relatively frequent steering operations in one direction are performed or when the interval between consecutive steering angle pulses is longer than a predetermined value, and producing a warning signal when steering adjustments which do not exceed the predetermined angle in one direction are repeated at a rate greater than a predetermined frequency, and a warning means for producing a visible or audible warning in response to the warning signal, whereby, the warning device can accurately detect dozing of the driver and produce a warning to make the driver wake up.
The Published European patent application No. 0061500 discloses a doze warning system which includes a circuit for producing a pulse signal representative of left- and right-hand steering adjustments, a circuit which counts the pulses of the pulse signal and produces a warning signal when the counter valve reaches a threshold value, and a circuit for producing a reset signal to clear the counter value when a difference between the number of pulse signals representative of left-hand steering adjustment and of right-hand steering adjustment exceeds a given value, or one of the left-hand or right-hand pulse signal counts exceeds a predetermined pulse number. The reset signal generating circuit detects steering adjustments exceeding the threshold value under normal driving conditions such as travelling along a curved road and produces the reset signal to inhibit production of this warning. By this reset signal generating circuit function, the warning system is prevented from malfunctioning.
The present invention intends to provide a drowsiness alarm system which can detect driver drowsiness more precisely and satisfactorily while eliminating occurrences of mis-judgment.